Microorganisms are widely used for industrially producing a broad range of useful substances, including alcoholic beverages, certain types of foods such as miso (i.e., fermented soybean paste) and shoyu (i.e., soy sauce), amino acids, organic acids, nucleic-acid-related substances, antibiotics, sugars, lipids, and proteins. These substances also find diversified uses, including foods, pharmaceuticals, detergents, products for daily use such as cosmetics, and a variety of chemical raw materials.
In industrial production of useful substances by use of microorganisms, improvement of productivity is one major topic of interest, and one approach therefor is breeding of microorganisms through mutagenesis or other genetic means. Recently, in particular, with advancement of microbial genetics and biotechnology, more efficient production of useful substances through gene recombination techniques attracts attention. In a known method for breeding productive microorganisms by use of gene recombination techniques, a transcription factor which regulates gene expression, in particular an RNA polymerase sigma factor, is potentiated. For example, in Pseudomonas fluorescens, the number of copies of a rpoD gene encoding a primary sigma factor (housekeeping sigma factor), which participates in transcription of genes essential to the growth during the vegetative stage, is increased, to thereby increase the production amount of an antibiotic, such as pyoluteorin or 2,4-diacetylphloroglucinol (see, for example, Non-Patent Document 1), and in Corynebacterium glutamicus, housekeeping sigA gene is overexpressed, to thereby increase the amount of fermentive production of L-lysine (see, for example, Patent Document 1).
In the above approaches, however, an increased expression of a housekeeping sigma factor is attained during the vegetative stage. Moreover, regarding microorganisms belonging to the genus Bacillus, such as Bacillus subtilis, no report has so far been published that states augmentation of a sigma factor leads to an increased production of useful substances.    Patent Document 1: WO 2003/054179    Non-Patent document 1: J. Bacteriol., 177, 5387, (1995)